The risk of injury to a nerve is a concern when performing surgical procedures, including minimally invasive procedures, within close proximity to the spine or spinal nerves. Surgeons increasingly rely on neuromonitoring techniques to monitor the nerves during such surgeries in order to avoid inadvertently injuring or contacting a nerve. Prior devices have been developed to help surgeons avoid contacting and damaging nerves during these procedures, but improvements are needed for enhancing the monitoring capabilities of those devices.
In some spinal surgeries, a patient's spine is accessed and viewed by anterior, posterior, or lateral approaches in which instruments for the surgery are advanced to the spine. When approaching the patient's spine, care must be taken to avoid nerves, in particular to avoid spinal nerves that exit the spinal cord at nerve roots extending through the spinal vertebrae. These spinal nerves include motor nerves, which control muscle activity throughout the body, and sensory nerves, which receive sensory input and relay the sensory input to the spinal cord and brain. During spinal surgeries, both motor and sensory nerves may be present in the muscle and tissue through which instruments are advanced to access the spine. Some techniques monitor muscle EMG responses during surgery to identify when a surgical tool is too close to a nerve. But those techniques do not address potential damage to sensory nerves, such as the genitofemoral nerve, that may also be near the surgical site. If damage to the nerves is not avoided, a patient may suffer post-surgery partial paralysis or pain resulting from the nerve damage.